How to check screens with an HDMI splitter

When you connect two monitors or TVs to an HDMI splitter, they usually show the same picture. Your computer may see the splitter as just one display, even though two screens are plugged in. That can make it hard to tell whether the splitter, a cable, or a screen is causing a problem.

The Screens tool shows the displays your computer reports, including their resolution and scale, and lets you run a color test on a selected screen. Use it to check what the computer detects, then compare what you see on each physical output.

Check the screens and splitter

1. Connect the computer to the HDMI splitter and connect each splitter output to a screen. Turn on the screens and choose the correct HDMI input on each one.
2. Open the Screens tool. Check how many displays it lists and note the resolution and scale shown for each.
3. If the tool lists more than one screen, run its color test on each listed screen. Check whether the colors and patterns appear on the physical display you expect.
4. If the tool lists one screen, run the color test anyway. Since a splitter normally duplicates one video signal, check whether the same test appears on every screen connected to it.
5. If one output looks wrong, disconnect that screen from the splitter and reconnect it directly to the computer, if you can. Compare the picture with the splitter in the signal path and with a direct connection.

To identify which physical screen is connected to a particular splitter output, unplug one output cable at a time and note which screen goes blank. Reconnect it before testing the next output.

What the result means

The tool lists one screen, and both displays show the test

This is normal for many HDMI splitters. A splitter copies the computer's signal to multiple outputs. It does not usually create separate desktops, so the computer and browser may report one display even when two screens show the picture.

The tool lists several screens

Your computer is reporting them as separate displays. Select each one in the tool's color test and compare the physical screens. If the test appears on a different screen than expected, use the operating system's display controls to identify or rearrange the displays. For help with screen names in Windows, see how to identify which monitor Windows is using.

One screen shows no picture

The computer may still detect the splitter as one display even if a splitter output, cable, or screen has failed. Check that screen's input and power, then test its cable and splitter output separately. A single-screen listing cannot confirm that every splitter output works.

The displays show a picture, but it looks different

The color test can help you spot differences such as a tint, missing colors, or uneven brightness. Some differences come from each screen's own picture settings, not the splitter. A color test also does not prove that a screen is calibrated or that its panel is defect-free.

The reported resolution seems too low

A splitter may negotiate a video mode that works for all connected screens. If one display supports a lower resolution or refresh rate, the source may use that shared mode. The resolution shown by the tool is the signal mode reported to the computer, and may not be the screen's native panel resolution. See how to check if a monitor is connected at the right size.

How to fix a screen or resolution problem

1. Check the screen input and power. Use the screen's own controls to select the HDMI input connected to the splitter. Make sure the screen is on, not asleep, and not showing a message such as No signal.
2. Reseat the HDMI cables. Unplug and reconnect the cable from the computer to the splitter, then reconnect each output cable. A loose connection can make a screen flicker, go blank, or show colored specks.
3. Test one output at a time. Connect one screen to the splitter and check the picture. Repeat with the other screen and output. If a problem follows one cable, replace that cable. If it follows one splitter port, the port may be faulty.
4. Check the display mode. In Windows 11, open Settings › System › Display and check the display arrangement and resolution. Under Multiple displays, choose a duplicate mode if you want the same picture on every screen. On macOS, open System Settings › Displays and check the available displays and mirroring options.
5. Check the splitter's power and supported modes. If your splitter has a power adapter, connect it. Check its instructions for the resolutions and refresh rates it supports, and compare those with the screens and computer output. Some splitters use an EDID setting, which tells the computer what video modes the connected screens support.
6. Restart the display connection. Turn off the screens and computer, disconnect the splitter from power if it has a power supply, then reconnect everything and start the screens before the computer. This can make the devices negotiate the video mode again.

What a browser test can and cannot confirm

The Screens tool reports display information that the operating system makes available to the browser. It can help you check the computer's reported displays, resolution, scale, and visible color output. It cannot identify a faulty splitter port by itself, measure the signal quality inside an HDMI cable, or tell you whether a screen's panel has a hardware defect.

For a clear comparison, test each splitter output with the same screen and cable where possible, then test each screen directly from the computer. If the fault follows the splitter when cables and screens are swapped, replace the splitter or contact its manufacturer.